An understanding of how taste stimuli are processed by the central nervous system (CMS)is important because the taste of food is a major determinant of ingestion. As such, it impacts the study of a variety of eating disorders including anorexia, bulimia and obesity. Of these, obesity looms large as a growing and costly societal problem in the United States that is nearing epidemic proportions. To further our understanding of taste processing, the present project is focused on the analysis of how temporal coding conveyes information about taste stimuli in cells contained in the nucleus of the solitary tract (NTS), the first central relay in the taste system. HYPOTHESES are: 1) The temporal structure of a taste response in the NTS conveys information about taste stimuli, and 2) The temporal pattern of activity in an NTS taste response can evokea taste-like sensation of predictable quality and hedonic value. r SPECIFIC AIMS : 1) Information contributed by temporal coding will be quantified by analysesof the electrophysiological responses in the NTS of anesthetized rats to taste stimuli that vary in concentration and taste quality, and are presented in mixtures, and 2) Generalization of conditioned aversions to lick-contingent electrical stimulation of the NTSwill be used to a) determine the critical features of the temporal pattern of electrical stimulation that are necessary and sufficient to evoke specific taste sensations and appropriate behavioral reactions, and b) construct a temporal sequence of electrical pulses which incorporates these critical features that, when used to drive activity in the NTS, will mimic the perceptual properties of a natural taste. SIGNIFICANCE: These experiments will provide data related to two aspects of temporal coding: the information conveyed by temporal patterns of responses and the function of a temporal code in taste perception.